Synchronized escapement clock



May 16, 939- HfE. WARREN 2,158,888

SYNCHRONIZED ESCAPEMEN'I' CLOCK Filed 'Dec. 19', 1934 Invent or:

Henry E.wamr en His Aobobne u.

I Patented May 16, 1939 UNITED STATES PATENT OFFlCE Warren Telechron Company,

Inc., Ashland,

Mass., a corporation of Massachusetts Application December 19, 1934, Serial No. 758,304

4 Claims.

My invention relates to timing devices such as clocks of the'type wherein the rate of operation of a spring driven clock is compared with the rate of operation of a synchronous motor and the lat- 5 ter is employed when in operation to synchronize the spring driven clock. The synchronous inotor may wind the spring of the spring driven clock and the latter has sufficient reserve and accuracy to maintain reasonably correct time over expected periodsv ,of failure in the alternatingcurrent supply to which the synchronous motor is connected.

According to the present invention, the spring clock is provided with a balance wheel-type of escapement and the balance wheel is so controlled by a resilient member operated from the synchronous motor 'to increase or decrease the rate of the escapement and bring it into a rate of operation which is synchronous with that of the motor. This controlling action is accomplished by brief interfering collisions between the balance wheel and resilient member but, should the synchronous motor stop, the resilient member always comes to rest out of contact with the balance wheel so that the latter is not interfered with but operates at its own time-keeping accuracy in case of and during failure of the alternating-current supply. The controlling arrangement is extremely simple and may be applied'at small expense to existing balance wheel escapement clocks.

The features of my invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. For a better understanding ,of my invention, reference is made in the following description to the accompanying drawing showing in Fig. l a perspective view of a spring driven balance wheel escapement clock equipped with my invention where the clock spring is wound by the synchronous motor that controls the escapement; Figs. 2 to 5, inclusive, illustrate different operating conditions of the resilient synchronizing device of Fig. 1 and its relation to the balance wheel; and Figs. 6 and '7 show modified forms of a synchronizing device that may be used. 7

Referring now to Fig. 1, I0 represents a selfstarting synchronous motor which is connected .to a regulated frequency source of supply II. This motor is connected through a geartrain l2 to one end of a clock spring at l3 and serves normally to maintain the spring in a wound condition. Preferably, the motor, when running at its proper rate, winds the spring at a slightly faster rate than it unwinds and provision is made, as by a friction clutch represented at II, to allow the winding drive to slip when the spring is substantially fully wound to prevent overwinding of the spring or of a slowing down of the synchronous motor.

The spring at I3 is connected through gears I 8 and IE to a suitable train leading to a timing device, such as the hour, minute, and sec ond hands I5, l6, and ll of a clock. .The usual back gears for the hour hand are represented at 20 and the gear train leading to the second-hand shaft 2| is represented at 22. A balance wheel type of escapernent consisting of escape wheel 23, verge lever 24, balance wheel 25, and control spring 26 is driven from shaft 2| and serves to control the rate of the clock as driven by the spring l3 in the usual way except when its action is modified by the synchronizing device now to be described. 1

The synchronizing device consists of a spring finger 21 which is rotated through a gear train 28 and shaft 29 from the synchronous motor In. The spring finger 21 consists of a spring wire secured to and coiled about the shaft, of the last gear 28 and has a radially extending portion with its outer end 3| bent forward to extend at right angles into the plane of balance wheel 25. The axis of rotation. of the spring finger and of balance wheel are parallel and spaced apart such that the end 3| of the spring-finger lightly touches the upper periphery of balance wheel 25 as the finger rotates past the balance wheel. Finger 21 rotates in a clockwise direction as here represented although this is immaterial. The shaft 30 to which finger 21 is secured is, of course, driven at a uniform speed by the synchronous motor and, when the motor I0 and the balance wheel 25 are operating at their correct rates, spring finger 21 makes one rotation in some synchronous relation with the period of oscillation of the balance wheel. In other words, a synchronous relation exists between the. cycles of operation of these parts. In order to give a practicable example, but not in the way of limiting the invention, it may be stated that spring finger 21 rotates at one revolution per second and the balance wheel makes two complete oscillations per second when both are operating at their correct rates. The outer end of spring finger 21 does not move at a uniform rate but its average rate of rotation is constant. There is provided a stationary pin or abutment 32 in the path of rotation of the outerend 3| of spring finger 21 against which the spring finger comes shortly before it reaches thebalance wheel. The

pin 32 holds the outer end of the spring finger 21 relatively stationary for a portion of a revolution oi the driving shaft 36 which causes a cer= tain amout of winding up of the spring about shaft 30 and a corresponding reduction in the length of the radially extending portion of the spring. This action continues until the spring arm has been deformed sufliciently for it to spring by pin 32. It then snaps past the periphery oi the balance wheel 25 at a relatively high rate of speed, and in doing so, momentarily collilies with the balance wheel.

The relationship of these parts and the action of the spring finger is more fully illustrated in Figs. 2 to 5, inclusive. in Fig. 2, the end 31 of the spring finger is approaching stationary In Fig. 3, contact has been made, the end 38 of the finger is being held relatively stationary while shaft so continues to revolve, tensloning and shortening the spring finger. the. l represents the condition where the spring is about to snap past the obstruction, it having been held here during nearly /4 revolution of shaft lit. Fig. 5 shows in full lines the approximate position of the spring 39 at the end or the snap action from which position it rotates uniformly with shalt 3t until it again contacts with ohstruction 3'2.

its indicated in dotted lines in 5, when the finger 2'17 snaps from pocution c to position c, it momentarily'collides with the balance wheel 28: at approximately position b and rapidly nasses on to position 0. This collision is not severe and the resiliency of the finger allows of its end wise displacement so as to pass by the balance wheel without difficulty. The collision ma ,how ever, have a tendency to modify the rate oi oscillation of the balance wheel, depending upon its phase position at the time of the collision.

' will he noted that the pin h s a co tact surface so that, by rotation oi the pin, e time during which. the free rotation of the is interfered with can he Such adjust noent will, or" course, vary the tension of the spring instant of its release and agreed at which it collides with the balance wheel and he used as a means of adjusting the device in The spring 2? may he of phosphor bronze i ah cut .ililtv or" an inch in diameter with a lever arm of the order or". one nalf inch.

lit will he evident that the linger iil imparts small periodic impulses to the balance wheel when the synchronous motor ls in operation should the synchronous motor stop in any position, the finger till will come to rest out oi contact with the balance wheel due to this lostmotion arrangement so that there is no inter ference-with the escapement mechanism of the spring driven clock and it then operates in a nonmal manner at its usual accuracy. fit a fact that, when small periodic impulses are imparted to an oscillating member like a halence wheel as above described, it these impulses have the same frequency or a subnoultipleor" the frequency of the oscillating body, the effect of the impulses tends to change the rate of the oscillating body, increasing or diminishing that rate according to the phase relation between the aieaess truancy oi vibration will be decreased and the clock rate will be reduced. 0n the other hand, it the impulses are provided in. such phase relation that they are in the same direction as the restoring force of the oscillating body, the rate will be accelerated and the clock will tend to run faster. In consequence of these facts, the appsratus described operates to synchronize the escapement as required to cause it to operate at a rate determined by the synchronous motor when the letter in operation.

This operation may be described as follows:

Collisions occur one each second as the spring finger 2T! snaps past the balance wheel. When the motor is first startedinto operation, the first collision may occur in any phase relation between the colliding parts with the parts moving in the some or opposite directions. If the tend ency oi the balance wheel m to be slightly fast and the collision occurs at a time to oppose the restoring three of the hair spring 28 with the parts moving in the some direction, the rate of the balance wheel will he reduced and each succeeriing ilnnulse will come at a later phase of the balance wheel until the phase position of the latter been retarded so that the impulses occur near the instant in time when the balance wheel passing; its midposition. As this rela tlon is cnnroeched, tic hnnuiees have less and less eilect until a condition of equilibrium is reached where the normal fast rate of the bal ance wheel exactly corrected on the average i337 ucriorlic impulses from the member 21.

r each rlliierent error in the normal rate of e wheel, it will have a diilferent phase when such equilibrium and correction in rate have heen established. Ii there is no r the normal rate oi" the balance wheel, l: e will come exactly as the balance wheel t its miripcsition when t e e will he no tendency oi the impulses to once wheele normal rate is slow inst, the contact phase position will octhe impulse force will he to of balance "wheel, which ts until the condition oi equilihriuinis established and the average rate of the lzalanc-e wheel is s ncluonous with the impulses and with the i eouency oi alternating cursupplied to uLiG synchronous motor. Generally the contact hetween the balance wheel and finger will occur when the contacting surfaces are moving in the same direction, because ii the contact initially occurs when these parts moving in the opposite direction, the tendency E quickly to shift the phase relation of the helance wheel until the collisions do occur at a time when the parts are moving in the same direction and then synchronizing regulation takes place as above explained.

The scheme does not require any exact adjustment of the synchronizing device or of the normal. rate of the escepement. The impulses imparted to the balance wheel should preferably he very feeble, not because this is essential for synchronization but because feeble impulses produce less shock and wear on'the delicate parts of the escanement mechanism. An ordinary escapement clock may be set to run at its fastest or slowest rate and be perfectly synchronized by means of this invention It will be noted that, ii the synchronous motor It stops due to a iailure in the source of supply, the synchronizing device 88 does not then interfere with the normal op- I eration of the escapement because it cannot stop in a position to rest against the balance wheel 25.

In Fig.6, I have represented another modification of the invention which I have found to operate very satisfactorily. In Fig. 6, the synchronizing impulse device strikes against the periphery of a wheel 33 on the same shaft as the balance wheel and which, therefore, may be considered as a part of the balance'wheel. The peripheral surface of wheel 33 may be knurled slightly. The synchronizing device consists of a spring 34 having its middle portion bent about a shaft 33. One end of the wire extends in a radial direction and has a bent end 36 that makes slight contact with the peripheryof wheel 33 as the end 36 is rotated past this wheel. The other end of the wire also extends in a radial direction and carries a small weight 31 at its outer end. A finger 33, extending from the side of a gear wheel 23 driven from the synchronous motor as in Fig. 1, is arranged to drive the wire 34 with the shaft 35 in a clockwise direction. The middle portion of the wire 34 may be secured to shaft 35 'and the latter is free to turn independently of gear 28. Thisconstitutes a lost-motion-driving connection between gear 23 and wire 34.

The weight 31 on the wire34is so arranged that, just about-the time the part 33. contacts with wheel 33 to impart an impulse thereto,

weight 31 reaches the vertical position'above shaft 35 so that, immediately after the impulse proximately the position shown in the drawing,

ready for another impulsing operation. v

This lost-motion-driving connection, which may take various forms, assures that,'in case the synchronous motor stops, the impulse part 33 will not come to rest in contact with wheel 33 and.

interfere with normal clock escapement operation while the synchronous motor is stopped.- The motion of the escapement alone will carry the wire past the dead-center. position in case the synchronousmotor stops just as contact is made between parts 36 and 33. Y The impulse imparted towheel 33 'may come while wire 34 is being driven through the overbalanced position by the synchronous motor, or the impulse may come at about the center of the gravity stroke. suchthat the'impulseiorce-is due to gravity acting on weight 31, in which case the wire 34 would be bent into the form shown in Fig. '1.

It will be understood that the .lost motion connection between the synchronous motor and impulse member may takea variety of forms so long as the arrangement is such that the impulse device cannot come to rest in a position to interfere with the escapement in case the synchronous motor stops in any positic.i.- Also, the movement of the impulsing device past the periphery of the balance wheel or its equivalent at the time of the impulse should be as fast or faster than the movement of the contacting surface of the balance wheel, itself, at the middle oi its oscillation. Theimpulsing device should in all cases have a rate of operation which'is synchronous with the rate of the balance wheel when the latter is corwheel in synchronous time.

, member positioned to engage the extremity of said arm at one point of its rotation and to momentarily hold it while its driving shaft continues .to rotate for a portion of a revolution,

thereby storing energy in the resilient arm and deforming it so that it snaps past the stop and forward said portion of a revolution, said resilient arm being positioned adjacent the oscillating part of said escapement mechanism such that'niomentary contact is made between the extremity of said arm and the oscillating part during the forward snapping movement of said arm to impart a rate-correcting impulse to said oscillatory part, said part having a period of oscillation when correct which is synchronous with the average rate 01' rotation of said arm. 1 v

2. In a mechanism. of the class described, a balance wheel, a synchronous motor, a control wheel driven from said motor, and a spring anchored at' one end to said control wheel and having its opposite end tree, the free end of said spring moving in the path otthe periphery of said balance wheel and being adapted to brush against the periphery of the balance wheel for giving a slight forward impulse to the balance '3. In a mechanism of the class described, a balance wheel, asynchronous motor, a control wheel driven from said motor, a spring anchored at one end to said controlwheel and having its opposite end free, the free end'oi said spring moving-in the pathof the periphery of said balance wheel and being adapted to brush against the periphery of the balance wheelfor giving a 1 slight forward impulse to the balance wheel in synchronous time, and means located in the path of travel ,of the free, advance of the balance heel for releasably en-- gaging and periodically retarding the same.

4. In a mechanism oi the class described, a

balance wheel, a synchronous motor, a control wheel driven by said motor, a coil spring'anchored atone end upon said control wheetand having its opposite end tree, said opposite end being bent outwardly to provide a hook adapted to travel in the path of the periphery of said balance wheel, and means located in the path 01' travel of said hook for periodically releasably en- 'to produce a brushing action thereagainst and give a slight forward impulse to the balance wheel in synchronous time, thus preventing the free end from stopping against the balance wheel, when current is cut on.

HENRY E. waannn.

of said spring and in i 

